For base stations in a wireless communication system, there has been increasing development of beam forming technologies that control directionality of multiple antennas to enable sharp emission of a radio wave in a specific direction. Using beam forming technologies reduces wave interference between terminals and thus enables wireless communications with more distant terminals. The beam forming technologies adjust phase errors between multiple antennas, thereby forming beams highly accurately. In order to form a beam highly accurately, antenna calibration for correcting phase errors between multiple antennas is performed.
For example, a technology that enables an OFDM wireless device to use a transmission signal as a reference signal, perform FFT processing on the reference signal to convert the reference signal into a signal in the frequency domain, and perform antenna calibration in the frequency domain is known. Related-art example is described in Japanese Laid-open Patent Publication No. 2005-348235.
The above-described technology, however, performs calibration by uniformly controlling the phases of signals over the whole frequency domain and therefore, when frequencies have different phase errors, respectively, it is difficult to correct the phase errors among antennas accurately. For example, when a signal occurs intermittently in each frequency, a phase error is calculated with respect to a frequency in which the signal does not exist can be calculated. This lowers the accuracy of calculating phase errors and thus it is difficult to accurately correct phase errors among antennas.